Protein synthesis by Escherichia coli infected with bacteriophage T4D

Abstract

Proteins made by E. coli cells infected with bacteriophage T4 were analyzed by a method which combined disc electrophoresis and autoradiography. The precursorproduct relationship between subunits and larger components (head, tail) was studied by taking advantage of the fact that the larger components cannot penetrate into the gel used in disc electrophoresis. These studies have shown that the early proteins are not controlled as a single homogeneous class all members of which are synthesized during the same time periods; instead, they start being formed and are shut off at various times during the early part of the infection process. Amber mutants in gene 30 (polynucleotide ligase-defective) synthesized a small amount of DNA, which was later degraded to a fraction soluble in trichloroacetic acid. The ligase-defective mutants were capable of synthesizing an almost normal amount of late proteins, whereas all other DNA-negative mutants, including a deoxycytidine triphosphatase(dCTPase)-defective mutant and maturation-defective mutants could not induce late protein synthesis. The dCTPase-defective mutant, which also synthesizes a small amount of unstable DNA, did not induce late protein synthesis even when the degradation of DNA was prevented.